Question about 2 stage AC/Heat Pump

I just moved into a new house with an
Amana 2 stage AC/Heat Pump. It is
controlled by a Honeywell HZ432
multi-zone controller. For AC it 1st
kicks in on stage 1 and if the
temperature is not satisfied in 10
minutes (selectable on the HZ432), the
2nd stage will kick in. This is
especially good as I am in an area where
the temperature doesn't usually get real
high in the summer (western NC
mountains) which will allow unit will
run a bit longer to remove more
humidity. Now that it's heat pump
season, the same 10 minutes applies to
the heat pump. In my way of thinking, I
would like to see the heat pump go
directly to stage 2 so you can get as
much heat as possible. I have heard
here, many people complain about heat
pumps and the drafty feel, etc.,
however, in this house, the HVAC guy got
is right as I don't notice these
problems. BTW, previously I've had a
gas furnace for many, many years so I do
know how that feels. Am I thinking
wrong here? What are your opinions?
Thanks.

'Pends on how you feel about economy vs faster response. There _may_ be
a way to change the operation to control on dT instead of/in addition to
simply time difference; the two-stage control on the geothermal system
we had did that; it was Water Furnace-supplied w/ the pump; I don't know
who actually built it.
You'll want to be sure to know whether that also is kicking in your
backup resistance heat as well, of course.
--

Thanks for the info. Actually, I wonder
about economy? Running on stage 2 will,
of course use more power, however, it
will get the heat delivered faster and
with less blower run time. The backup
heat is actually a 2 stage propane
furnace (Goodman). So far this season,
it has only come on during one cold
morning and I think it came on because
the outside coil was deicing.

I doubt the time will be sufficiently reduced to be observable on energy
savings. I'd expect the added load to more than compensate while
running at the second stage. Remember, it's a fixed dH to raise the
temperature a specific amount irrespective of time. You'd have to have
actual performance figures to know how linear the power cost is vs heat
output at the two performance levels to get a computed estimate. Other
than that, it would take monitoring usage each way over a significant
time such that day-to-day variability would average out.
BTW, in marginal area, might want to consider an interlock on the backup
heat so it only comes on below (say) 20F or somesuch. Did that w/ the
geothermal system in E TN by adding an external thermocouple into the
control loop calling for the backup. W/ the geothermal (rather than
air-exchange) it made it essentially a non-starter that was almost never
needed. Air-exchange are much improved since the one that system
replaced, but am sure it would still have come on more often w/ a newer
one than w/ the ground source but wouldn't have been just a cool-morning
thing.

Whatever rings your chimes. If you find a big blast of heat satisfying,
it's your house and your electric bill. The most efficient heating
system is one that never shuts down or cools off. A lower powered heat
pump will also create less hot and cold spots in the house. The second
stage is there for colder days when the smaller heat pump just won't do
the job. If you want to set the heat pump to go directly to stage 2,
you will pay a few extra bucks for heat, but other than that I don't see
it will do any harm.

--
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with my first name and last initial.

Am I the only one wondering what sense it makes for the heat pump to
always start on stage 1 for 10 mins, then move to stage 2? It would
seem in any properly sized system, 10 mins of AC run time would rarely
be enough to cool the house even 1 degree. And in any case, it
would seem the thermostat would be smart enough to have a better way
of figuring out what stage to start at, eg the current temp delta, how
hot it is etc. Seems strange to waste 10 mins on stage 1 if the
house is 85.

I was _presuming_ (dangerous, I know... :) ) that there's more to the
control logic than simply time but wasn't interested enough to either
try to look up the thermostat datasheet or ask the OP... :)
I think this is one of those that has a "self-learning" mode that is
based on several inputs the demand dT being only one and they also use
previous heating/cooling "histories" to try to find a site-specific
strategy. How well they'll work in practice will be dependent on just
how clever the programming was and the suitability to the particular
installation.
I've never actually had one; only read about some of the logic designs
in a few of the engineering trade magazines. My general impression has
been they seemed too gimmicky to be of much real value in comparison to
more simple control schemes w/ setback so that I really wondered if they
could demonstrate any actual advantage to speak of or whether were more
marketing/feature-rich driven.

Well, it is based only on time, when the
HZ432 is being used to control
the heat pump or AC. You can set it
from a few minutes to, I think, 15 or
20. I agree that I can't see "wasting"
10 minutes waiting for heat and then
go to stage 2. I think the thermostat
has multiple stages of heat, but it is
only 3 stages and I have 4. I am
thinking that it the whole thing would
be better controlled by the thermostat
than the HZ432. I have looked at
various thermostats that have seem to do
a better job of detecting when
to bump up to the next stage. I think
my next thing to do will to call
Amana/Goodman and also Honeywell. I
hate calling Honeywell because
you get a call center in Asia.

We sell Amana and have installed a number of two stage HP's. We
typically use a White Rogers stat, though I can't tell you the model off
the top of my head and don't feel inclined to go check right now.
Anyhow, I have often thought about exactly the same thing. The WR stat
does "learn" cycle times and how long t takes to sense any temp change
when it decides to kick stage two in. On Amana two stage you drop about
1/3 capacity in low stage. It would be easy enough to rig a HP to only
run in high on heating. I have brought up the idea, but we have never
had any customer complaints, so never tried it. Anyway, all you would
have to do is have a relay that is powered from the 'Blue" wire on the
stat (which powers in heat mode and is usually only used with Rheem/Ruud
HP's) Just have that relay jump Y1 and Y2 togther when it is powered ,
which is only in heat. BTW, I have toyed with the idea of putting a 16
SEER two stage Amana 3 ton HP in my house, but as long as the antique
Trane keeps on going I probaby will never do it. (Waiting for the
distributor to get one dinged up with only cosmetic damage that they
will make a deal on (: Larry

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